The bug makes it difficult for the phone to carry out one of its most basic tasks of answering a call. The delayed display issue means that users can't swipe the on-screen button to answer a call.

A scan of Apple's support forums show that scores of iPhone X owners seem to be suffering from the same problem.

"Whenever the incoming calls come on my iPhone X the display doesn't [light] up, it vibrates and rings but the display doesn't turn on, it only turns on say after good 5 to 6 secs," wrote one confused user.

"When receiving incoming call on iphone x its only ringing and vibrate there is no display on screen," another said.

Apple said it was "looking into these reports."

The bug is another embarrassment for Apple, which has justified the iPhone X's £1,000/$1,000 price tag with futuristic features such as facial recognition, an advanced camera setup, and a high-end OLED display. But the phone has been plagued with problems, with Apple putting out a software fix for devices that temporarily stopped working in cold weather. And a small number of users reported a green line appearing on the side of their iPhone X screens.